黄土性土壤剖面不同层次N_2O浓度的原位监测

In-situ measurement of N_2O concentration from profile of loess soil

用土壤探头法对黄土性土壤玉米-小麦轮作体系下不同剖面层次N2O浓度变化进行了3a的田间原位监测。结果证实了黄土性土壤深层反硝化作用的存在,且N2O浓度有着明显的时间和空间变异。表现为N2O浓度受土壤气候条件(温度和降水)和生产管理措施的影响,丰水年明显高于亏水年;在降水或灌溉后出现瞬时N2O浓度峰。由于小麦和玉米生长特点和作物生长季气侯特点的差异,玉米生长季土壤剖面各层N2O浓度显著高于小麦生长期土壤剖面各层的浓度。统计分析结果表明:土壤剖面中不同土层N2O浓度的变化对照处理为60cm≈90cm≈150cm>30cm>10cm,而施肥处理为60cm>90cm≈150cm>30cm>10cm。深层土壤N2O的主要来源是土壤的反硝化作用,施肥显著地增加各土壤层次N2O的产生量。

Using soil probe techniques, we in situ measured changes of N2O concentration at different soil depths of loess soil profile in a long term field experiment were measured from 1999 to 2001. The experimental results proved denitrification in deep layer of loess soil. Meanwhile, N2O concentration in soil profiles had remarkable temporal and spatial variation. The annual N2O concentration variation changed with the climate condition and management practice. There was higher N2O concentration in soil profiles in the year when the annual precipitation was higher than normal. N2O peaks often appeared after the irrigation or rainfall. The average N2O concentration during corn growing season was greater than that during winter wheat season, mainly due to the higher temperature and rainfall amount in the summer season. The N2O concentration in the soil profiles were in the order of 60cm ≈ 90cm ≈ 150cm 〉 30cm 〉 10cm for control treatment, and those in the order of 60cm 〉 90cm ≈ 150cm 〉 30cm 〉 10cm for N fertilized treatment. The subsoil denitrification was the main N2O source of subsoil in loess soil. Appling nitrogen fertilizer would definitely increase N2O concentration in soil profiles.